Unless Congress takes action, one in four families with children — up from one in 22 last year — will owe up to $3,640 in additional federal income tax come next April.

Few of them realize that their taxes have increased, because Congress has not voted to raise taxes. Instead, Congress let a tax break expire. That break limited the alternative minimum tax, which takes back part of the tax cuts sponsored by President Bush.

Mr. Bush has asked Congress to temporarily restore the tax break, known as the A.M.T. patch. He has also asked Congress to extend another break that lowered the tax rate on most investment income to 15 percent.

Leading Republicans and Democrats agree that there is simply not enough money to do both. Congress was unable to reach an agreement on tax breaks before adjourning for vacation earlier this month.

The expiration of the A.M.T. patch and the tax break for investment income almost balance each other out this year, according to the Tax Policy Center, a nonprofit organization whose computer model of the tax system has been deemed reasonable and reliable by the Bush administration. The impact will be felt primarily among taxpayers of two different income levels.

The A.M.T. will cost Americans who earn $50,000 to $200,000 nearly $13 billion more next April. That is about how much people who earn more than $1 million will save because of the break on investment income like dividends and capital gains. Both figures were provided by the Tax Policy Center, which is a joint project of the Brookings Institution and the Urban Institute.

Taking action on either measure will require more government borrowing, adding to the federal budget deficit, which is projected to reach $423 billion this year.

Comments

I'm all for it. The faith-based (data-ignoring) abstinence programs should be among the first to go. And no more bridges to nowhere in Alaska, thanks. And maybe Wyoming isn't in need of a lot of Homeland Security funds, as much as we'd hate to see terrorists engage in cow-tipping there, in the absence of crowded urban metropolises.